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Urban Road User Charging Online Knowledge Base

Why is It Important To Set Objectives?

Road pricing is a controversial policy instrument, and it is therefore important to demonstrate the purposes for which it is being introduced. Moreover, road pricing can serve a range of objectives, including congestion relief, environmental enhancement and revenue generation, each of which may be best served by a different design of road pricing scheme. For both these reasons it is important for a city considering road pricing to be clear as to its objectives.

When those objectives have been specified, they can be used as an input to scheme design (Chapter 3), as the basis for predicting (Chapter 6) the impact of and appraising (Chapter 10) alternative design options and evaluating (Chapter 15) the performance of implemented schemes. The objectives are thus a priority in the scheme’s conception and have different functions, as shown in Figure 2 1.

Objectives are usually expressed in terms of a desired end point, such as an improved environment, or greater safety. These rather abstract concepts are sometimes difficult to understand. An alternative approach is to focus on the problems (pollution, casualties, congestion) which need to be overcome, and express objectives in this way. Another approach is to specify indicators (such as the level of CO2 emissions, or fatal accidents, or delay per km) against which objectives are to be assessed. This can further be developed by setting targets for achievement in terms of these indicators. Such quantified approaches can aid understanding and subsequent appraisal and evaluation, but care is needed that the right indicators are chosen and that the targets are set at an appropriate level (May, Page and Forrester, 2008).

There is a case, in the interest of increased acceptability (Chapter 12) for keeping the objectives simple and focused. The reference to the London scheme as a congestion charge is a case in point. However, this can prove a limitation if the scheme is subsequently modified to meet other objectives, as has been the case with the proposed use of congestion charging in London to penalise high emission vehicles. Where more than one objective is being pursued, a given design may be more effective at meeting one objective (e.g. congestion relief) than another (e.g. revenue generation). In such situations trade-offs need to be made, and some sense is needed of the relative importance of the objectives.

Even where objectives limited in number, there will be constraints on their achievement (for example seeking pollution reduction subject to not adversely affecting the economy, or achieving congestion relief subject to not causing undue inequities). These constraints can be treated as objectives in their own right, and need to be reflected in scheme design and appraisal. Thus the list of objectives considered in the design process may well be much longer than that used for public consultation.